Green’s Dictionary of Slang

net n.1

[backsl.]

the number ten.

[US]Sun (NY) 10 July 29/4: Here is a genuine letter written in theives’ slang [...] Meet me at net to darkmans in blloming slum near the old padding ken to get off the swag.
[UK]Partridge DSUE (1984) 786: [...] 1851.